Some of the best powder I have in my stock is from the 60's. It's not black powder and is used in one of my wife's unmentionable rifles. I worked up a bunch of loads for this gun with a lot of different powders and this particular one shot lights out above brand new lots of similar powder. So if smokeless can hold up well for nearly 60 years then black should last a whole lot longer. Good score on that much black for free.